I am looking at a blob of water. Not pond water. Not pool water. Just ordinary H2O floating about in what appears to be zero gravity. And inside its wetness there’s a passenger, a goldfish, a very alive goldfish …

… that is trying desperately to escape—or so it seems. It flings itself at the blob’s edge, pushing it outward.

Then it tries to get out the back. That’s its head peeping through.

Then it charges and stretches the skin of the bubble almost to the breaking point.

But try as it might, it can’t get free. Poor little fish, I thought. It’s a prisoner.

I found it, the fish and its floating prison, on my favorite fluid dynamics blog, FYFD, which is